#Health :Millions of people worldwide have to go to emergency rooms for asthma attacks every year because they are breathing dirty air,

Polluted air may trigger as many as 33 million asthma-related emergency room visits globally each year, a new study finds.

"Millions of people worldwide have to go to emergency rooms for asthma attacks every year because they are breathing dirty air," said study lead author Susan Anenberg, of George Washington University in Washington, D.C.

"Our findings suggest that policies aimed at cleaning up the air can reduce the global burden of asthma and improve respiratory health around the world," added Anenberg, an associate professor of environmental and occupational health.

Asthma is a chronic airway disease that makes it difficult to breathe. It affects about 358 million people around the world, the study authors noted in a university news release.

The new findings suggest emissions from cars and other sources may play a significant role in asthma attacks, Anenberg's team said.

For the study, the researchers analyzed hospital emergency department data from 54 countries and Hong Kong, and used sophisticated technology to gauge air pollution levels.

The investigators tied ozone to between 9 million and 23 million asthma-related emergency department visits worldwide each year (up to 20 percent of total asthma ER visits). Ozone is produced when vehicular, power plant and other types of emissions interact with sunlight.

Another 5 million to 10 million asthma emergency department visits every year were linked to fine particulate matter -- microscopic pollutants that can lodge deep in the lungs.

South and East Asian countries, notably India and China, accounted for about half of the asthma emergencies, the researchers said.

While air pollution is less severe in the United States, ozone still contributed to between 8 percent and 21 percent of asthma ER visits, the researchers said. Particulate matter led to 3 percent to 11 percent of asthma ER visits, according to the study.

"We know that air pollution is the leading environmental health risk factor globally," Anenberg said in the news release.

Yet about 95 percent of the world's population lives with unsafe air, the researchers said.

The report was published Oct. 24 in the journal Environmental Health Perspectives.